People do it all the time with Ivy and Haswell stuff, delidding the processor. It can make or break your CPU for a high overclock, which is why they do it. Some will pop the lid (not hard to do, from what I've read), put a new TIM on, then place the lid on and clamp it (force of the cooler holds the lid on). Others will do a bare-die delid, where they just put the TIM on the die and put the cooler directly onto it, which gives a better drop in temps than putting the lid on.
There are two schools of thought as to why delidding even works:
1. Crap TIM from Intel
2. The cavity in the lid is a bit too much, so the die and lid don't quite touch, meaning the heat doesn't transfer as well to the die and cooler. (more-accepted of late)